ORCHARDS 2 ORegon CHild Absenteeism due to Respiratory Disease Study 2 SUMMARY Background: Influenza is common in school-aged children, has high attack rates, and is a leading cause of school absenteeism. It is associated with substantial morbidity, mortality and economic costs. Because influenza is efficiently spread within school settings, rates of school absenteeism have been proposed as a component of early warning systems. The lack of specificity, however, has limited the effectiveness of this method. During the first three years of ORCHARDS, we have shown significant and high correlations between: (1) influenza cases within absentee children (SI) and medically-attended influenza (MAI) in the surrounding community, (2) influenza-like illness absenteeism (a-ILI) and SI, and (3) a-ILI and MAI. We have created and tested a simple modification of an existing and widely-used electronic school information system (ESIS) to automatically report a-ILI on a daily basis, and used this information to accurately identify influenza outbreaks in the community. Program Goal: The goal of ORCHARDS-2 is to expand the assessment of this system to assess for different strains and timing of season influenza outbreaks. In addition, the level of transmission occurring within household of index SI cases will be evaluated. Methods: We will use parental reporting of symptoms into a telephonic absence reporting system and an algorithm within the Infinite Campus ESIS for daily absenteeism assessment. We will actively recruit at least 300 children absence due to respiratory infection from the Oregon School District, Dane County, Wisconsin, in each of four years. We will use home visits to collect detailed demographic, household, epidemiologic and symptom data, and nasal and NP/OP specimens for virological testing. Nasal specimens will be tested using SOFIA RIDT. NP/OP specimens will be transported to the Wisconsin State Laboratory of Hygiene for influenza rT-PCR testing and for the presence of other respiratory viruses using a Luminex Multiplex PCR platform. We will recruit at least 240 households with ill children for transmission assessment. All household members will self collect nasal specimens on day 0 and 7 for influenza rT-PCR and provide detailed illness data. The temporal patterns of a-ILI will be compared to influenza surveillance based on MAI within the surrounding community. Rates of within-home transmission of influenza will be calculated. Significance: School-based influenza surveillance provides an opportunity for extremely early detection of influenza in a community. School to home transmission is likely to expand outbreaks. Coupling cause-specific absenteeism with RIDT, with PCR confirmation, allows for inexpensive, rapid identification of seasonal and pandemic influenza.